There is a large world market for hand-held wireless communication devices, and it is always of concern to design these systems to operate with the lowest amount of power. Advances in miniaturization of hand held devices such as cell phones, pagers and PDAs are often limited by power source constraints, including battery sizes. Many cell phones and small consumer audio appliances with limited power configuration are equipped with transducers such as speakerphones that project the speech to the listener instead of being directly coupled to the ear. Much of the current focus in industry technology has been on better speaker design or more efficient resourcing of current drain in the power amplification stage. No energy conservation schemes directly operate on the audio alerts to generate alerts. Alerts are typically used to notify users of incoming calls, pages, text messages, calendar alarms and more.
Recent demands in today's market for increased quality in the production of audio alerts have led to deploying digital techniques. With reference to medical alerting devices, the conventional embedded low-power medical device alerts must be sufficiently loud so as to draw the attention of the device-holder. Conventional on-the-body medical alert devices are used intermittently, since the device-holder may be performing other activities and needs to be notified only when a medical-alert is necessary. In most cases, the holder is not paying attention to the device.
In addition, conventional medical device alerts (such as those used on pagers) use a single tone to alarm the individual: for example, a runner's heart rate monitor or a wristwatch to measure speed. Typically, the tone is about 1 KHz, since informal listening tests reveal that the frequency is annoying enough to draw the attention of the user and solicit a response. However, the tone is not optimal for loudness while maintaining a low power requirement.
Further, studies have shown that the psychoacoustic and audiometric data varies from listener to listener. Stated differently, a system optimized for loudness for a given listener often is not optimized for another listener. Accordingly, a need exists to supply a system which can be customized to a particular user.